The present invention relates to a device for very large conduction heat transfers without a concomitant mass transfer. The present invention can be employed in any situation where a heat pipe might otherwise be employed, but the present invention is superior to a heat pipe in several respects. The invention has particular utility in the rapid removal of heat from fluids which are radioactive (such as in nuclear reactors), as well as from fluids having undesirable chemical properties and which must remain isolated from the environment.
Although the present invention is quite distinct from a heat pipe, heat pipes nevertheless provide a convenient reference point for purposes of comparison. As is well known, in principle a heat pipe is an elongated cylinder containing a working fluid which changes between the liquid and the gas phases during operation. The heat pipe absorbs heat at one end by vaporization of working fluid, and releases heat at the other end by condensation of the resultant vapor. The liquid condensate returns to the heat absorbing end by capillarity through a capillary structure, for example covering the internal face of the cylinder. The process proceeds continuously, and the resultant heat transfer of a heat pipe may be 10,000 times or more higher than the conductive heat transfer of a solid copper or silver rod.
While heat pipes have found wide application, they nevertheless have two disadvantages in particular which are overcome by the present invention. One disadvantage of heat pipes is that the working fluid within the heat pipe continuously recirculates during operation from one end to the other. Thus there is mass transfer from one end to the other. This is particularly disadvantageous in the case of heat removal from radioactive fluids because radioactivity is in effect carried from one end of the heat pipe to the other as the entire volume of working fluid becomes radioactive. A second disadvantage of heat pipes is that a given heat pipe, depending upon the particular working fluid selected and the internal pressure, can function only over a particular range of temperatures. Specifically, the temperature at the heat-absorbing (relatively hotter) end of the heat pipe must be at least high enough for vaporization of liquid phase working fluid, and the temperature at the heat-releasing (relatively colder) end of the pipe must be at least low enough for condensation of gas phase working fluid.
In addition to avoiding these two disadvantages, the present invention provides much higher heat transport rates. Embodiments of the present invention can provide heat transport rates several orders of magnitude greater than that of existing heat pipes.